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SS6612 数据表(PDF) 11 Page - Silicon Standard Corp. |
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SS6612 数据表(HTML) 11 Page - Silicon Standard Corp. |
11 / 16 page www.SiliconStandard.com 11 of 16 Rev.2.02 12/06/2003 SS6612 PIN DESCRIPTIONS PIN 1: FB- Connected to OUT to get +3.3V output, connected to GND to get +5.0V output, or using a resistor network to set output voltage rang- ing from +1.8V to +5.5V. PIN 2: LBI- Low-battery comparator input inter- nally set at +1.23V to trip. PIN 3: LBO- Open-drain low battery comparator output. Output is low when VLBI is <1.23V. LBO is high impedance during shutdown. PIN 4:CLSEL-Current-limit select input. CLSEL= OUT sets the current limit to 1.0A. CLSEL=GND sets the current limit to 0.65A. PIN 5: REF- 1.23V reference voltage. Bypass with a 0.1 µF capacitor. PIN 6: SHDN- Shutdown input. High=operating, low=shutdown. PIN 7: BATT- Battery input and damping switch connection. If damping switch is unused, leave BATT unconnected. PIN 8: GND- Ground. PIN 9: LX- N-channel and P-channel power MOSFET drain. PIN 10: OUT- Power output. OUT provides bootstrap power to the IC. APPLICATION INFORMATION Overview The SS6612 is a high-efficiency, step-up DC/DC converter, featuring a built-in synchronous rectifier, which reduces size and cost by eliminating the need for an external Schottky diode. The start-up voltage of the SS6612 is as low as 0.8V and it operates with an input voltage down to 0.7V. Quiescent supply current is only 20 µA. In addition, the SS6612 features a circuit that eliminates inductor ringing to reduce noise. The internal P-MOSFET on-resistance is typi- cally 0.3 Ω to improve overall efficiency by minimizing AC losses. The output voltage can be easily set; by two external resistors for 1.8V to 5.5V; connecting FB to OUT to get 3.3V; or connecting to GND to get 5.0V. The CLSEL pin offers a selectable current limit (1.0A or 0.65A). The lower current limit allows the use of a physically smaller inductor in space- sensitive applications. PFM Control Scheme A key feature of the SS6612 is a unique minimum- off-time, constant-on-time, current-limited, pulse- frequency-modulation (PFM) control scheme (see BLOCK DIAGRAM) with ultra-low quiescent current. The peak current of the internal N-MOSFET power switch is selectable. The switch frequency depends on either loading conditions or input voltage, and can range up to 500KHz. It is governed by a pair of one- shots that set a minimum off-time (1 µs ) and a maximum on-time (4 µs ). Synchronous Rectification Using the internal synchronous rectifier eliminates the need for an external Schottky diode, reducing the cost and board space. During the cycle of off- time, the P-MOSFET turns on and shuts the N- MOSFET off. Due to the low turn-on resistance of the MOSFET, the synchronous rectifier signifi- cantly improves efficiency without an additional ex- ternal Schottky diode. Thus, the conversion effi- ciency can be as high as 93%. Reference Voltage The reference voltage (REF) is nominally 1.23V for excellent T.C. performance. In addition, the REF pin can source up to 100 µA to an external circuit with good load |
类似零件编号 - SS6612 |
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类似说明 - SS6612 |
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